Wireless sensor network (WSN) is an important component of the Internet of Things (IoT) effort. It provides seamless connectivity and control capabilities to surrounding infrastructure and facilities. It also provides access to real world data through measuring and monitoring the environment. However, applications with stringent reliability constrains have not fully adopted the WSN. For instance, delay is a major concern in many manufacturing and other sensitive facilities. In such environment, sensor nodes must convey the data to the sink node in the monitoring center as soon as it becomes available. Such data collection could be periodic or aperiodic process. Once the data is available from all or subset of the nodes, the control center may choose the appropriate action.
Thus, it is necessary to develop specialized networks that are capable of accommodating applications with a strict delay and reliability requirements. Recently, several standards have been developed to address some issues that improve the reliability of WSN such as interference, delay, and integration with current and future standards. For instance, WirelessHart and 802.15.4e provide MAC layer that uses TDMA, where the scheduling time is divided into periodic intervals, called time-slots, and frequency hopping (FH) to combat delay and interference. All nodes are assumed to have a synchronized time clock so that they know the starting and finishing times of each slot.
U.S. Pat. No. 8,005,002 B2 assumes that the data is available at all the nodes at the beginning of the scheduling. However, this assumption is not satisfied in industrial and other delay sensitive applications. Furthermore, the U.S. Pat. No. 8,005,002 B2 prior work focuses on the schedule size. However, minimizing the schedule size in the constrained non-uniform release time does not minimize the end-to-end delay.
Therefore, there is a need to address scheduling schemes that address the delay sensitive scheduling problem in wireless multi-hop convergecast networks and many-to-one networks.